The aim of this study is to determine the utility of nicotinamide in preventing or delaying the clinical presentation of insulin dependent diabetes mellitus in individuals at an increased risk of developing the disease. Nicotinamide is a water soluble group B vitamin which has been effective in preventing onset of diabetes in animal models, has produced promising results in uncontrolled trials in humans, and may have some benefit in prolonging beta cell function in recently diagnosed patients with insulin dependent diabetes. Within the last year, we have enrolled 8 more patients, ages 5 to 40 years, into a randomized, blinded trial to prevent diabetes using nicotinamide (vitamin B3) or placebo. Within the next few months we are planning to enroll possibly 6 more patients. In the state of Texas, there are 6 centers with local investigators screening their families with Type I diabetes. Another state has joined with us in this international study.The study as a whole has done very well and has almost reached the appropriate number of subjects to show a significant difference between the 2 groups should there be one at the point of the interim analysis. The international participating investigators meet yearly to review the study.